The invention relates to a suspension apparatus, and more particularly, to a suspension apparatus such as a suspension beam or suspension tong having movable shackles provided therewith which can be automatically engaged with and disengaged from the hook of a crane by a remote control.
The use of a suspension apparatus between the hook of crane and a load is well known in a crane in transporting a load of substantial length and weight such as a roll used in the manufacture of steel. The suspension apparatus has a pair of movable shackles pivotally mounted thereon for suspending the apparatus from the double hook of the crane. An apparatus for automatically engaging or disengaging the movable shackles from the double hook of the crane is also known. For example, Japanese Patent Publication No. 22, 741/1973 issued to Zenichi Kohama et al on July 9, 1973 discloses in FIG. 10 thereof that a pair of movable shackles 1, 2 are normally urged by springs 3, 4 to their reset position in which they are removed or open, but can be rotated toward each other against the resilience of the springs 3, 4 to reach their set position in which they hold the double hook 7 of the crane therebetween, as the double hook 7 is placed on a pair of drive levers 5, 6 which extend from each of the movable shackles toward the other shackle to cause the gravity of the hook to rotate the drive levers 5, 6 about their pivots 8, 9 on the movable shackles 1, 2. The disclosed apparatus includes a locking device 10 which locks the pair of movable shackles 1, 2 when they reach their set position. Subsequently, as the double hook 7 moves upward, the movable shackles 1, 2 can be received in the opening of the hook. The locking device 10 comprises a knock plate 11 which is adapted to be moved by each of the drive levers 5, 6, a pair of locking arms 14, 15 engageable and disengageable from a pair of locking pins 12, 13 secured to the movable shackles 1, 2, and a clutch 16 of a special design which operatively connects the knock plate 11 with the pair of locking arms 14, 15. The movement of the knock plate 11 as the crane hook 7 moves downward initially causes the pair of locking arms 14, 15 to engage the locking pins 12, 13 on the corresponding movable shackles 1, 2, respectively, thus locking the movable shackles 1, 2 in their set position. However, when the crane hook 7 moves upward subsequently and then moves downward, the operation of the knock plate 11 for the second time, (the knock plate 11 being reset by a spring as the crane hook 7 moves upward) causes the pair of locking arms 14, 15 to release the corresponding movable shackles 1, 2 in their position which is the same as their set position.
In the disclosed apparatus, each of the movable shackles 1, 2, as they are released from the locking device 10, is operated upon by the resilience of the springs 3, 4 which causes the shackles to return to their reset position. However, because the crane hook 7 remains in contact with the drive levers 5, 6 secured to the movable shackles 1, 2, the resetting operation takes place only gradually as the crane hook 7 moves upward. The problem then is the fact that an upward movement of the crane hook 7 through an increased stroke is necessary in order to reset the movable shackles 1, 2 from their released position. However, this is undesirable because the likelihood that the crane hook 7 may be inadvertently engaged with the movable shackles 1, 2 during its upward movement increases with an increase in the stroke. This is attributable to the facts that the drive levers 5, 6 on the respective movable shackles 1, 2 must be able to rotate through an angle which is equal to the angle of rotation between the reset position and the set position of the movable shackles 1, 2, and that the drive levers 5, 6 must extend far enough for contact with the crane hook.